SUMMARY Measured values of the transmission of amorphous films as a function of the objective aperture and film thickness can be described by a single‐scattering theory for unfiltered and zero‐loss filtered images in the electron spectroscopic imaging mode of a transmission electron microscope. The theory can be applied to estimate the gain of contrast by zero‐loss filtering for specimen structures larger and smaller than the chromatic aberration disc.

SUMMARY The ratio of inelastic‐to‐elastic total cross‐sections has been measured in an energy‐filtering electron microscope for different elements. Formulae for the transmission of elastically and inelastically scattered electrons in part I were used to calculate the optimum conditions for a Z‐ratio contrast in the electron spectroscopic imaging mode. Structure‐sensitive contrast can be observed for all non‐carbon atoms in biological sections when filtering with an energy loss at ΔE ∼ 250 eV below the carbon K edge. Model experiments with evaporated layers of different elements on a carbon film allow measurement of the contrast increase. Filtering with the carbon plasmon loss shows a lower phase contrast than with zero‐loss filtering. This can be explained by calculating contrast transfer functions for inelastically scattered electrons.

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